Table 3.
Summary of papers included in the meta-analysis
| Paper | Subjects | Methods | Measurement of sun exposure | Confounders adjusted for | Main results* |
|---|---|---|---|---|---|
| Cohort studies | |||||
| Robsahm, 2004 | 39,583 Norwegians, aged 25-94 years, diagnosed with prostate cancer |
Identified from Norway Cancer Registry between 1964 and 1992. 16,457 deaths from prostate cancer. |
Residential sun exposure, based on mean annual UV radiation calculated for region II-VIII relative to region I. |
age at diagnosis, birth cohort, period of diagnosis, stage of disease at diagnosis, occupational sun exposure, childbearing pattern, educational level. |
Relative risk (95% CI) of prostate cancer death, compared with lowest group of UV exposure (residing in region I): Region II = 1.00 (0.90-1.11); III = 1.02 (0.94-1.12); IV = 0.99 (0.90-1.08); V = 1.16 (1.06-1.28); VI = 0.98 (0.90-1.07); VII = 1.10 (1.02-1.21); VIII = 0.98 (0.88-1.07). p-trend = 0.28. |
| John, 2007 | 3528 non-hispanic white men aged 25- 74 years, sampled from US population, followed by enrollment into the NHANES I follow-up study cohort |
Initial baseline interview and dermatologic examination in 1971-1975. 161 cases of prostate cancer (59 fatal cases) with information on sun exposure. Identified from combination of self-report, hospital records & death certificates. |
Self-reported occupational or residential exposure |
age | Relative risk (95% CI) of prostate cancer, compared with the lowest exposure group (both never, rare or occasional) was: Incidence One frequent = 0.80 (0.52-1.24); Both frequent = 1.05 (0.70-1.58). Fatal incidence One frequent = 0.46 (0.21-1.02); Both frequent = 0.70 (0.35-1.40). |
| de Vries, 2007 | 13,541 white male skin cancer patients from southeastern part of the Netherlands |
Identifed from Eindhoven Cancer Registry, diagnosed since 1970 till 2005. 272 prostate cancer patients (61 stage III and IV cases). |
Rates of invasive prostate cancer in skin cancer patients (as a proxy for high sun exposure) compared with rates in general population. |
age, period of diagnosis | Standardized incidence ratio (95% CI) of prostate cancer, compared with general population: Incidence = 0.89 (0.78-0.99); Fatal incidence = 0.73 (0.56-0.94). |
| Case control studies | |||||
| Freedman, 2002 | 97,873 cases were deaths from prostate cancer in 24 states of US. 83,421 controls were deaths, excluding cancer and certain neurological diseases. |
Identified from National Cancer Institute, the National Institute for Occupational Safety and Health and the National Center for Health Statistics database of information recorded on death certificates between 1984 and 1995. |
Residential exposure, based on annual mean daily solar radiation for state reported as residence and birthplace, US Weather Bureau data |
age, sex, race, occupation, physical activity, socioeconomic status |
Odds ratios (95% CI) of prostate cancer mortality, compared to low exposure: Medium = 0.89 (0.86-0.91); High = 0.90 (0.87-0.93). |
| John, 2005 | 450 nonhispanic white cases of advanced prostate cancer, aged 40-79 years, from San Francisco regional cancer registry, during 1997-2000. 455 controls recruited by random digit dialling, matched by age. |
In-person inverviews and structured questionnaire, reflectometer measure. |
Sun exposure index, based on relative difference between constitutive and facultative skin pigmentation as a measure of cumulative lifetime sun exposure |
age, family history, month of pigmentation measurement |
Odds ratios (95% CI) of advanced prostate cancer, compared to lowest quintile (Q1): Q2 = 0.87 (0.58-1.30); Q3 = 0.80 (0.53-1.20); Q4 = 0.95 (0.64-1.42); Q5 = 0.51 (0.33-0.80). P-trend = 0.02. |
| Skin reaction to summer midday sun exposure |
age, family history, month of pigmentation measurement |
Odds ratios (95% CI) of advanced prostate cancer, compared to ‘moderate to severe sunburns’: Mild sunburns = 0.86 (0.65-1.14); No sunburns = 0.72 (0.46-1.11). P-trend = 0.1. |
|||
| Rukin, 2007 | 528 white cases of prostate cancer, mean age 70.2 years, from urology clinics at University Hospital North Staffordshire. 365 controls with benign prostatic hypertophy from same clinics. |
Self-administered questionnaires of lifetime UV exposure |
Average daily sun exposure (hrs per day) since age 20 |
age, skin type | Odds ratios (95% CI) of prostate cancer = 0.78 (0.72-0.85) |
| Skin type | Odds ratios (95% CI) of prostate cancer, compared to Q4 (readily tans): Q3 = 0.74 (0.51-1.07); Q2 = 0.73 (0.49-1.09); Q1 (never tans) = 0.47 (0.26-0.86). P-trend = 0.024. |
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*
Results as reported. For the meta-analysis, results are inverted to make scales comparable where necessary.